Combustion system for an intensified burning of solid, liquid or gaseous fuels in an annular combustion space



1959 .1. CERMAK COMBUSTION SYSTEM FOR AN INTENSIFIED BURNING OF SOLID,LIQUID OR GASEOUS FUELS IN AN ANNULAR COMBUSTION SPACE Filed Aug. 2,1957 INVENTOR JOSEF CEIPMAK United States Patent- COMBUSTION SYSTEM FORAN INTENSIFIED BURNING 07F SOLID, LIQUID R GASEOUS FUELS IN AN ANNULARCOMBUSTION SPACE Josef Cermak, Prague, Czechoslovakia Application August2, 1957, Serial No. 67 5,838

Claims priority, application Czechoslovakia August 11, 1956 Claims. (31.110-28) The present invention relates to a combustion apparatus forachieving intensified combustion of solid, liquid or gaseous fuel-s inan annular combustion space.

By the term intensified combustion a high intensity of combustion isunderstood, which-expressed in calories released in 1 m of the volume ofthe combustion space per hour-exceeds 1.10 kcal./m.. /hour.

Devices for achieving the intensified combustion of solid fuels havealready been proposed, wherein the burning content of the furnaceeffects a whirling (turbulent) motion. Such devices operate as a rule asslagging devices, i.e. the mineral residue of the fuel flows out of thecombustion space in the form of a liquid slag.

Typical of a great number of such known devices are combustion chambersof the 'socalled cyclone or whirling type. Their common feature is acylindrical combustion space, either vertical or horizontal, suppliedwith fuel and combustion air, either at one point at the circumferenceand approximately in tangential direction or through the end Wall so asto cause the burning contents flowing through the combustion space toassume a helical movement.

The products of combustion leave the furnace either through an upper orlower central aperture or through an aperture in the wall of thecylindrical jacket. The ratio of the height or length of the cylindricalcombustion space to its diameter varies within the range of about ,113,up to about 5:1.

In those cases Where the fuel and combustion air are supplied at thecircumference of the cylindrical space in the combustion chamber, thisis effected practically at one point of the circumference, moreparticularly through a relatively narrow slot at the circumference ofthe cylinder. This causes the disadvantageous irregular flow and burningout of the fuel in such combustion chambers.

When fuel is supplied at one point of the circumference, theconcentration of the oxidising agent is different at all points alongthe circumference of the cylindrical chamber, and is highly dependent onthe momentary volatile contents of the fuel, on the specific surface ofsame (i.e. on the surface corresponding to a unit weight of the fuel)and in particular on the thermic history of the fuel grains (i.e.temperature as a function of the time) during their passage through thecombustion space.

It has also been found that, in the above described existing combustionchambers, the burning contents of the furnace flow through thecombustion space irregularly. The explanation for this phenomenon liesin the fact that for a part of the time these burning contents flowthrough the combustion space in the regular way until suddenly ashortcut takes place, that is, the fuel and air proceed along theshortest way between the inlet to the combustion space and the outlettherefrom. This shortcutting causes the escape of unbnrnt combustiblegases and increased escape of mineral combustion residue.

Owing to this fact a combustion chamber of the described known typecannot be fully thermally loaded ice Le. a specific thermal intensity ofabout 5.10 kcaL/mfi/ hour cannot be exceeded.

In some combustion devices of the cyclone type, the above drawback isobviated by a careful distribution and control of the amount of thesecondary air supplied to the individual parts of the cyclone combustionspace. Considering the varying quality of the fuel this solution isdisadvantageous in operation with respect to the changing amount of theair required, and is therefore undesirable.

Careful measurements have also shown that, in the vicinity of thecentral aperture in the central part of the cylindrical space, thecontents of the same rotate as a wheel so that the circumferentialvelocity is directly proportional to the distance from the center ofrotation. On the other hand adjacent to the outer circumference of thecylindrical space the movement is such, that the circumferentialvelocity is dependent on the radius in accordance with the hyperbolic'law (principle of Whirl conservation). The intense whirling which isindispensable for an intensification of the combustion process occursmerely between the two above mentioned spaces i.e. in a relatively smallvolume.

All these facts and experiences have recently led to the search foranother aerodynamically more favourable shape of the combustion chamber.Thus, for example, for small power generating units, in particular formobile units, a system for burning solid fuel in a helical con1- bustionspace with a cooled metal wall has been developed. This system is freefrom from the above mentioned drawbacks and allows therefore theconstruction of small devices having a high combustion intensity andhigh efiiciency. In the further development of the cotmbustiontechnique, in particular for large stationary power generating units,the use of combustion chambers in annular form has been considered, thelatter offering a further possibility for increasing the efiiciency ofthe space combustion.

The present invention utilises the last mentioned possibilities for anintensified burning of solid, liquid or gaseous fuels in a combustionspace which is generally toroidal or annular shape, being eithercircular in any radial cross section (a so called tours) or having anyother suitable radial cross section.

The main object of the present invention is to provide a combustionapparatus having a toroidal or annular combustion space arranged toensure favourable conditions for mixing and burning fuel and theseparation of mineral residue so as to practically eliminate, orsubstantially reduce, the above mentioned drawbacks of the knowncombustion chambers.

The combustion chamber according to the present invention ischaracterised by the following three basic features:

(a) A central supply of fuel by means of fuel nozzles, which arearranged at the inner circumference of the toroidal or annularcombustion space and open into this space in suitably chosen directions.

(b) The provision of a distribution head having the fuel admittedtangentially therein and arranged above the center of the toroidal orannular combustion space, said distribution head being connected withthe fuel nozzles by means of tubes or flow channels and these fuelnozzles being arranged so as to make a sharp angle With the direction ofrotation of the fuel stream.

(c) Arranged around the outer circumference of the toroidal or annularcombustion space is a distribution space for the combustion supportingmedium with one or more inlets and with a plurality of outlets openingapproximately in tangential direction into the combustion space.

The combustion system according to the present invention shows a numberof other particular features which will be apparent from the ensuingdescription.

The accompanying drawing shows in a simplified diagrammaticrepresentation a combustion apparatus which is an illustrativeembodiment of'the invention.

Fig. 1 is a vertical section taken along the plane II of Fig. 2; and

Fig. 2 a horizontal section taken along the plane II-II of Fig. 1.

The illustrated combustion apparatus has a combustion space 7 in theshape of a torus for burning solid fuel mixed with air and which isdefined by an annular shell having its axis arranged vertically with aC-shaped cross section opening radially inward toward the vertical axis.

The apparatus further comprises the following main parts:

A distribution head 2, a system of tubes 4 terminating in fuel nozzles 6opening into the combustion space 7, and a combustion air distributionspace 9.

Fuel carried by a minimum amount of primary air enters through atangential inlet 1 into the distribution head 2 which is preferablycentrally arranged above the combustion space. The rotating stream offuel and primary air is distributed by a cone 3 to the inlet portions ofthe tubes 4, which feed the fuel nozzles 6. The tubes 4 are inclinedwith respect to the central axis in the direction of rotation of thestream so as to exert the least possible hydraulic resistance to thelatter and so as to have the maximum possible static pressure before thefuel nozzles 6. The tubes 4 may be provided with transparent parts 5(e.g. of glass) through which the flow of fuel in the individual tubesmay be observed.

The fuel nozzles 6 are arranged at the inner circumference of thetoroidal or annular combustion space 7, preferably directly above theoutlet 14 for the hot combustion products, so that the entering fuelmixture is heated up by the hot combustion products to a hightemperature, just before the entry of the fuel mixture into thecombustion space.

The fuel preferably issues from the fuel nozzles 6 into the combustionspace 7 in the direction indicated by the arrow 8 shown both in Fig. l(in a vertical plane) and in Fig. 2 (in a horizontal plane). It isapparent, that this is an upwards slanting direction and at the sametime also approximately tangential to the direction of rotation of thecontents of combustion space.

The secondary combustion air is introduced in the example shown throughan inlet 11 into the distribution space 9 and from the latter throughthe outlets 10 which open approximately in tangential direction 13 intothe combustion space 7.

The hot exhaust gases leave the combustion space in the direction of thearrows 12 towards the outlet, through which the slag is also discharged.Arranged in front of the outlet for the exhaust gases is an annular dam15, which ensures that a certain amount of liquid slag always remains inthe combustion space.

Due to favourable conditions of outlay and operating conditions a highlyeflicient and uniform combustion process is obtained in all parts of theapparatus. Such a combustion process cannot be achieved in the knowncylindrical combustion spaces.

Prior to its entry into the combustion space 7 fuel is heated up to ahigh temperature at which it begins to gasify. The fuel is fed to thecombustion space so as to assist to the highest possible degree therotational movement of the contents of the combustion space. At the sametime each particle of the fuel is forced to follow a relatively longpath and a shortcut, as in cylindrical combustion chambers, cannot hereoccur. A premature impact of the ignited fuel particles against the wallof the heating surface and the difficulties caused thereby are thus alsoeliminated.

Under the influence of the rotational movement of the contents of thecombustion space, the largest particles fly along a curved path 8 up tothe contact with the wall, as shown in Fig. 2; this results in anextension of their paths and of the time during which they remain in thecombustion space.

An intense sorting of the fuel particles according to the size ofparticles takes place simultaneously. The smallest grains are held upfirst in the rotating stream, and are ignited and burn out immediatelyin the zone 1. Larger particles fly along a longer path and are laterignited and burnt, in the zone II. The largest particles pass throughthe entire space and strike against the outer wall along which theycontinue their movement in zone III. These largest particles are ignitedlast and also burn out last. However, since the largest particles remainin the combustion space much longer than the average time during whichthe gaseous content of the combustion space remains in the latter, suchlarge particles have ample time to burn out completely.

As a result of this size distribution of the particles in introducedfuel stream and further due to the fact that the fresh fuel is.introduced along the entire inner circumference of the combustion spacesubstantially in a uniform way (through a relatively high number of fuelnozzles 6) a perfect utilisation of the entire volume of the combustionspace for an intense combustion is achieved. The combustion space oftoroidal or annular form, which, in the example described above, is inthe shape of a torus, may therefore be thermally loaded to a far higherdegree than any other combustion space.

The quick rotary movement of the contents of the combustion space, whichis far quicker than in a cyclone type furnace, is made possible byadmitting the secondary combustion air, which forms the major proportionof combustion air, into the combustion space at its outer circumferenceand in a uniform. manner. The uniform admission of this air insubstantially tangential direction ensures a high speed of rotation ofthe contents of the furnace which results in a centrifugal force as wellas the separation of coarser fuel grains and their longer stay in thefurnace. By this advantageous method of admission of fuel and combustionair it is possible not only to ensure the ignition and burning out ofthe fuel at the right time, but also to achieve a high specific thermalloading of the furnace and a high efficiencythereof, as a result ofwhich the device is relatively small and of light weight.

A highly favourable influence on the combustion is exerted by the fact,that the larger and largest fuel grains fly in a quick sequence throughthe streams of the oxidising agent supplied at the outer circumferenceof the combustion space. This advantage is not achieved in otherintensified rotational furnaces.

As shown by the arrow 8 in Fig. l the fuel leaving the nozzles 6 ispartially projected upwards against the ceiling of the combustion space.This ensures. permanent supplying of the top portion of the combustionspace wall with fresh slag and the maintenance of a deposit thereof in asufficient thickness.

The dam 15 serves to maintain a layer of slag in front of the outlet 14,said slag retaining the mineral residue from the combustion, separatedby centrifugal action.

The above described example does not, of course, exhaust thepossibilities of various arrangements of the combustion system withinthe framework of the present invention. Thus, for example, either all orpart of the highly preheated secondary air (combustion air) may be fedto the distribution head 2 so as to cause a partial degasification ofthe fuel prior to its entry into the combustion space. Further, obviousstructural arrangements may be employed in the combustion apparatusaccording to the invention in order to adapt such apparatus forintensified combustion of liquid or gaseous fuels' I claim:

1. A combustion apparatus comprising an annular shell arranged with itsaxis extending substantially vertically and having a generally C-shapedcross section opening radially inward toward said axis and defining acombustion space, said shell having an opening at the center of thebottom thereof for the downward discharge there through of products ofcombustion from said combustion space, means for supplying a mixture ofprimary air and fuel to said combustion space including a series ofinlet nozzles arranged approximately in a circle adjacent said verticalaxis of the annular shell and opening into the latter in directions thatslant upwardly and are approximately tangential to said circle in whichthe nozzles are arranged, and means for supplying secondary air to saidcombustion space including a. series of inlet orifices distributed alongthe outer periphery of said annular shell and opening into saidcombustion space.

2. A combustion apparatus as in claim 1, wherein said inlet orifices forsupplying secondary air to said combustion space open into the latter indirections that are approximately tangential to said outer periphery ofthe annular shell in the same directions as said inlet nozzles forsupplying the mixture of primary air and fuel into the combustion space,so that the mixture of primary air and fuel and the secondary air areintroduced tangentially into said combustion space at the inner andouter peripheries of said shell in the direction of rotation of thecontents of said combustion space.

3. A combustion apparatus as in claim 2; wherein said means forsupplying the mixture of primary air and fuel to said combustion spacefurther includes tubes extending to said inlet nozzles through thecentral portion of said annular shell so that the mixture of primary airand fuel flowing through said tubes to said inlet nozzles is heated bythe burning contents of said combustion space.

4. A combustion apparatus as in claim 3 wherein said tubes have portionsextending close to said central opening in the bottom' of said annularshell.

5. A combustion apparatus as in claim 4; wherein the bottom of saidannular shell curves upwardly toward said central opening to define adam around the latter for retaining a quantity of slag at the bottom ofthe combustion space.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain Feb. 9, 1955

